Stud welder



June 30, 1942. E. F. NELSON 2,287,818

STUD WELDER Filed May 51,'` 1940 s sheets-sheet 2 l g CoNTAcroQ 1INVENTOR RNEY 5 Sheebs-Sheet 3 E. F. NELSON STUD WELDER Filed May 5l,1940 June 30, 1942.

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Patented June 30, 1942 UNITED STATES PATENT OFFICE 9 Claims.

This invention relates to mechanism for effecting electric butt-weldsbetween metallic ob- J'ects.

The disclosure of invention herein embodies improvements over thestructures of my prior Patent No. 2,191,494, issued Feb. 27, 1940, forStud Welder, and my prior Patent No. 2,217,964 issued Oct. 15, 1940, forStud Welder.

It is an object of the present invention to provide welding apparatus ofthe class described in which the duration of the arc between the partsto be joined together may be very accurately adjusted and uniformlymaintained.

Another object of the invention is to provide, in welding apparatus of'the class described whose operation, to perform a welding cycle, may beinstituted by depressing a manually actuated control element, safetymeans which becomes operative during a welding cycle to preventaccidental turning on of the welding current during intervals in whichthe apparatus is being handled between welding cycles.

The invention possesses other objects and features of advantage, which,together with the foregoing, will be specically set forth in thedetailed description of the invention hereunto annexed. It is to beunderstood that the invention is not to be limited to the specific formthereof herein shown and described as various other embodiments thereofmay be employed within the scope of the appended claims.

Referring to the drawings:

Figure l is a View, partly in side elevation and partly in verticalsection, showing the stud Welder and its support.

Figure 2 is a horizontal sectional view of a portion of the support. Theplane in which the view is taken is indicated by the line 2-2 of Figure1.

Figure 3 is a horizontal sectional view of the lower portion of thesupport and stud Welder. The plane in which the view is taken isindicated by the line 3-3 of Figure 1.

Figure 4 is a vertical sectional View taken in a plane passing mediallyand longitudinally through the stud welder. The various parts of thestructure are shown in the positions they occupy just prior to startingthe welding cycle to make a weld. An electrical diagram showing theconnections between the various current carrying parts of the apparatusis included as a component part of the view.

Figure 5 is a horizontal cross-sectional view of a portion of the studWelder. The plane in which the view is taken is indicated by the line5--5 of Figure 4.

Figure 6 is a view similar to Figure 4 showing the positions of parts ofthe mechanism after institution of and during the welding cycle.

Figure 7 is a vertical sectional view of the timing unit for variablyadjusting the duration of the welding cycle.

In construction work, particularly in shipbuilding, where steel deckplates are overlaid with wooden planking, it has been the custom in thepast to first place the planking, drill holes through the planking andthe underlying steel plate and then place in these drilled holessuitable bolts for permanently securing the planking to the plate. Theplacement or removal of such retaining bolts required the services oftwo workmen since one had to hold the bolt against turns ing from oneside of the assembled structure while the other workman applied andcinched the nut from the other side of the structure. Such procedureconsumed considerable time and seriously slowed down production. Inaddition to this, only a slight loosening of one or more of the boltnuts permitted Water to seep, through the bolt holes, below deck, Inlater and improved construction a series of threaded studs wereelectrically butt-welded directly to the deck plates thus eliminatingthe through bolt holes and the services of the holder-on for securingthe hold-down bolt against turning. This procedure, however, requiredthat the planking, after the studs were placed, be properly positionedover the studs and tapped so as to impress the ends of the studs intothe planking, whereupon the latter was removed, bored to provide thestud apertures, and then replaced on the studs. The hold-down nuts werethen threaded on to the studs. This series of operations consumed nearlyas much construction time as the older through-bolt system. In myaforementioned prior applications it was pointed out how considerabletime could be saved in sheathing steel structures with wood or othercovering material by first pre-forming in the covering the desirednumber of stud apertures, then placing the coveringin its ultimateposition on the steel structure and then electrically butt-welding thestuds to the underlying steel through and concentrically of theapertures in the covering. Thus, immediately after the studs are weldedin place, the holddown nuts may be applied to the studs and tightened.

It is vitally important, since the weld which joins the stud to thesteel deck plate is being made in the plank aperture and is thereforeobscured from the view of the operator, that the distance the stud isdrawn away from the plate, in creating the welding arc, and the lengthof time that the arc is permitted to burn, to effect raising of theopposed surfaces of the stud and plate to fusion temperature, be veryaccurately and uniformly maintained for each successive weld ifuniformly strong unions are to be had between the studs and plate. Inprior devices the welding head, in which the stud forming one electrodeof the welding circuit was held, was supported on a stand or tripodwhich rested on the upper surface of the planking with the studprojecting downwardly into the planking aperture. Suitable stops onguides in the welding head permitted the stud, after contacting the deckplate to be drawn upwardly a predeter mined distance to establish thearc gap. However, since the thickness of the planking may vary more orless, it will be seen that variations in the are gapvmay' also occurwhich may adversely affect the quality of the resulting weld.

In the welding heads of my prior applications, I disclosed the use of adashpot in which oil was displaced by a moving piston to time theduration of the welding arc. This arrangement operated satisfactorilyand accurately maintained the timing if relatively small diameter studswere of the arc which adversely affected the strength of the weld.

Another undesirable feature inherent in prior stud welding mechanisms isthat no provision is made, during intervals when the operator ishandling or conditioning the mechanism between welds, for preventing theheavy welding current from being turned on accidently, should theoperator happen to inadvertently depress the starting trigger with whichmost of these mechanisms are equipped, and seriously burning theoperator if his hands are in contact with a current carry-v ing piece ofthe apparatus.

All of these undesirable features have been overcome in the device ofthe present invention. First, the welding mechanism may be quickly setfor each weld to produce a uniform arc gap regardless of the amount ofvariation in thickness of the planking; second, the timing of the weldis accomplished by a device remote from the scene of the weld where itwill not be affected by heat absorbed by the welding head; and, third, asafety device is included in the mechanism which positively preventsturning on of the welding current until the mechanism has been fullyconditioned to make the succeeding weld.

In detail, I have shown in Figures 1, 4, and 6, a steel deck plate 8overlying which is wooden Iplanking 9, which is to be secured to theplate 8, having an aperture II therethrough into which the threaded studI2, which is to be butt-welded to the upper surface of the deck plate 8in the position in which it is shown in Figure 4, may be inserted. Asuitable shouldered nut, not shown, is adapted to be threadedly engagedwith the stud, after the latter has been welded in position. for tyingthe planking and the deck plate together. The plate 8 forms oneelectrode of the welding circuit while the stud I2 forms the otherelectrode thereof and it is the function of mechanism termed the weldinghead and generally indicated by the numeral I3 in Figure 1, to, rst,hold the stud, as shown in Figure 4, in contact with the surface of theplate until the welding current is turned on, secondly, to draw the studaway from the plate, as shown in Figures 1 and 4, to create an arc gap,and, thirdly, after the end of the stud and surface of the plate havebeen brought to the melting point by the arc flame, to quickly join themelting members so as to eect the union thereof.

During the welding cycle the main portions of the welding head arerigidly supported in a iixed position. This is accomplished by asuitable supporting structure such as that fully described in myapplication Serial No. 410,793, filed Sept. 13, 1941, comprising a baseI4, which rests on the upper surface oi' the planking 9, having thereinan opening I6, through which the stud I2 may be raised and lowered, andan upwardly rising tubular post- I1 which is secured, at its lower end,to the base by a screw I8. Telescoping over and slidable axially of thepost I1 is a tube I9 having therein a pair of spaced brackets, eachcomprising a split collar 2| secured to the tube by means of a clampscrew 22 and having extensions 23 which are attached to the welding headI3 so as to position the latter axially concentric with the base openingI8. A key 24, projecting through a suitable opening formed in andadjacent the lower end of the tube I9 and entering a keyway 26 cutlongitudinally. in the periphery of the post I1, serves to preventrelative rotation between the tube and -post and thereby to maintain thestud I2 in axial concentricity with the base opening I6. The upper endof the tube I9 extends into a bored recess 21 formed in a hub 28 havinga radially projecting grip 29, and the hub is split axially of therecess 21 and provided with apertured lugs 3| bearing a clamp bolt 32for clamping the tube I9 in the recess 21. The grip 29 provides a handhold for the operator so that he may raise and lower the welding headwith respect to the base I4.

Means is provided for securing the welding head in a selected elevatedposition. Secured at its upper end in the recess 21, by the clamp bolt'32, and positioned within the tube I9, is a collet sleeve 33 whichextends downwardly in axial concentricity with the tube I3, terminatesadjacent the lower end of the latter, and telescopes within the post I1.The lower end of the collet sleeve is provided with a plurality ofcircumferentially spaced, axially extending slots 34, and with a taperedcountersink 36 forming a, continuation of the internal bore 31 of thesleeve. This construction provides a plurality of radially flexiblelingers at the lower end of the collet sleeve. Positioned concentricallywithin the collet sleeve is a control rod 38 secured to the lowerthreaded end 39 of which is a frusto-conical plug 4I complementary withand engaged in the tapered countersink 36 of the collet sleeve. Theupper end 42 of the control rod passes slidably through a centralaperture formed in a washer 43 which rests, in a fixed position spacedfrom the upper end of the collet sleeve, against a shoulder formedwithin the bore of the sleeve. A nut 44 is threaded on the extreme upperend of the control rod and interposed between the nut 44 and the washer43 is an expansion spring 46. The spring 46 ls for the purpose of urgingthe control rod 38 upwardly in a direction axially of the collet sleeve33 so as to draw the plug 4| into the countersink 38 thereby radiallyurging the flexible lingers into tight frictional engagement with theinner periphery of the post I1. This locks the movable tube I9 and thepost I1 against relative longitudinal displacement and also holds thewelding head firmly in the desired elevated position. In the event thata welding head of considerable weight is being used, the peripheralsurfaces of the fingers contacting the post I1 may be knurled so as tobite into the surface of the post and thereby obtain maximum gripbetween the engaged parts.

Means is provided for releasing the connected post I1 and tube I9, topermit raising and lowering of the welding head I3, and means is alsoprovided for partially counterbalancing the weight of the welding headto assist in the raising thereof. Positioned within the recess 21 andbetween the concentric tube I9 and collet sleeve 33, is a short tubularfiller 41 and the assembled tubular members are provided with alinedapertures which form, as is best shown in Figure 2, an opening 48through which passes a release lever 49. A pin 5|, having its oppositeends seated in holes drilled into the tube I9 and ller 41, extendstransversely across the opening 48 and through a journal hole bored inthe release lever so that the latter is pivotally mounted on the pin.The inner end of the release lever is bifurcated to provide a pair ofngers 52 which bearagainst a washer 53 secured to the control rod 38,and the outer end 54 of the release lever is extended substantiallyparallel to and outwardly substantially equal to the length of the grip29. When the operator desires to raise or lower the welding head, heextends one or more of the fingers of his hand resting on the grip 29 toen- The length of this arc gap is usually only a small fraction of aninch and is chosen to produce the desired arc llame depending upon theamount of welding current available. It will be seen that if thedistance 'between the upper surfaces of the deck plate 8 and theoverlying planklng 9 is uniformly the same in each aperture II in whicha stud is to be placed, the welding of a large number of studs may becarried forward in the knowledge that the arc gap of each successiveweld will be the same as that of the previous welds.

gage the outer end 54 of the release lever and to draw the said outerend of the lever towards the grip. This causes the fingers 52 to movethe control rod 38 downwardly so as to move the plug 4| out of thecountersink 36 thereby releasing the radial pressure of the colletlingers against the inner wall of the post |1. With the base maintainedin contact with the surface of the planking 9, the tube I 9 and thevarious parts, including the welding head, carried thereby may beshifted longitudinally of the post |1 to any desired position. Releaseof the lever extension 54 will again set the friction lock to secure thewelding head in'xed relation to the base I4. An axially expansiblespring 56, positioned within the tube I9 and interposed between the endsof the post I1 and the ller tube 41, respectively, serves, when thefriction lock is released, to urge the tube I9 and its connected partsupwardly thereby partially counterbalancing the weight of the weldinghead I3.

As was stated above, a uniform arc gap should be maintained insuccessive welds if each weld is to possess the maximum of strength. Aswill be explained in detail later, the mechanism of the welding head ispre-set so that, as shown in Figure 4, the lower end of the stud |2rests on the upper surface of the deck plate 8. When the welding currentis turned on, action takes place within the welding head. and while thelatter is held rigidly fixed with relation to the deck plate, whichmoves the stud I2 to a position elevated above the deck plate, as shownin Figure 1, to4

create the arc gap between the stud and plate.

However, due to variations in thickness in the planking 9 and thepossibility of raised seams, protuberances or depressions in the surfaceof the deck plate 8 happening to coincide with one or more of theapertures the depths of all of the apertures will not be alike. Usingpreviously known equipment, work was seriously retarded by therequirement that the workman, before making each weld, measure the depthof each hole and set the welding head support to provide the desired arcgap. With the apparatus of my invention, it is only necessary, after thewelding head has been conditioned, or cocked, as shown in Figure 4, toplace the base |4 in position on the planking 9 over the aperture andrelease the friction lock between the post I1 and tube I9 so as to allowthe stud I2 to descend into the aperture until it just touches thesurface of the deck plate. The lock may be then re-engaged since thestud is now positioned to provide the correct length of arc gap when itis drawn away from the plate by the mechanism within the welding head.It will be therefore seen that a workman may quickly set the apparatusfor each individual hole in which a stud is to be mounted withoutappreciably cutting down his production speed.

The welding head comprises a preferably cast metallic casing 51 havingat its lower end a plurality, preferably three, of bosses 58 each beingprovided with threaded sockets 59 which receive screws 6I for securingthe lower bracket extension 23 to the casing 51. The threaded sockets 59also may be used, when the welding head is being employed without itssupporting structure shown in Figure 1, to receive the threaded ends ofcoaxial rods whose lower ends may rest against the planking so as toform a tripod for supporting the welding head in axially verticalposition. Such a support may be employed when the welding head is beingused in cramped quarters in which there is not sufficient headroom forproper operation of the supporting structure of Figure 1.

Means is provided for supporting the stud I2 so that it may be moved,independently of the movement thereof permitted by the adjustablesupporting structure described above, along a path away from and towardthe surface of the deck plate 8. A chuck 6I is provided, the lower endof which is centrally bored to form a socket, which receives the upperend of the stud l2, and is provided with longitudinally extending slots62 which form, at the lower end of the chuck, a plurality of flexiblefingers 63 gripping the stud and frictionally holding the latter in thechuck socket. The opposite end of the chuck is provided with a threadedbore 64 in which the correspondingly threaded shank 66 of a plug 61 isengaged. Surrounding the periphery of the plug 61 is an insulatingsleeve 68 having a peripheral flange 69 thereon. An insulating disk 1|overlies the end of the plug 61, adjacent tthe insulating sleeve 66 andis provided with an annular skirt 12 which overlies a retaining flange13 on the plug. Surrounding the insulating sleeve 68 and disk 1I is acap 14 having an annular lip 16 engaging the shoulder of the flange 69and which is internally threaded 'and engaged with a correspondinglythreaded flange 11 formed at one end of a tubular ram 18 so as to clampthe plug 81 to the ram. 'I'he provision of the disk 1| and the sleeve 68electrically insulates the stud AI2 and its supporting chuck from theram 18 and the remainder of the mechanism which will presently bedescribed.

The ram 18 is mounted so as to freely slide axially of and within astationary tube 19, the latter being provided with a fixed key 8| whichoperates in a slot 82 formed in the ram so that motion of the ram isconfined to axial directions, the key 8| serving to prevent any relativerotational movement between the ram and the tube. The end of the tube 19adjacent the flange 11 of the ram is spaced from the latter a distancecorresponding to the length of arc gap desired so that, when the ram ismoved upwardly until the flange 11 contacts the end of the tube 19 thearc gap 83, shown in Figures 1 and 6 will be established between thelower end of the stud I2 and the upper surface of the deck plate 8. Theopposite end of the tube 19 is provided with a pair of axially extendingdiametrically opposed slots 84,'best shown in Figure 5, and isexternally threaded to engage the threads in the bore of a hub 86 formedat the end of the casing 51. This mounts the tube in fixed relation -toand concentric with the casing within the bore 81 thereof.

A circular disk 88, best shown in Figure 5, is provided with a pair ofconcentric arcuate apertures 89 and with bridge portions 9| passingthrough the slots 84 of the tube 19, the portions 92 of the tube betweenthe slots passing through the disk' apertures 89. The disk is thusmounted concentrically with the tube and is free to be moved axiallythereof in the slots 84. The disk is provided with a central countersunkaperture which receives the conical head 93 of a bolt 94 which extendsconcentrically of the ram 18 toward the lower or chuck end thereof. Aspacer tube 96, on the bolt 94, passes slidably through a centralaperture formed in a wall 91 formed in the ram 18 intermediate the endsthereof and a coil spring 98, concentric with the bolt, is interposedbetween the wall 91 and the disk 88. A relatively larger tube 99 is alsocarried by the bolt 94 and this latter tube and the spacer tube 96 aresecured in place by means of a nut and washer |02 secured to the extremelower end of the bolt. A coil spring |03 concentric with the bolt hasits respective ends engaged with the ram wall 91 and the washer |02. Theshoulder |04 provided between the smaller and larger tubes 96 and 99acts as a stop against which the ram wall 91 may impinge to limitdownward movement of the ram. The outer periphery of the disk 88 isprovided with a circular shoulder |06 onto which is pressed one end of atubular skirt |01. mounted on the tube 19 and has an end flange |09engaging the disk 88, and a similar sleeve III is slidably mounted onthe lower end of the tube 19 and has a peripheral flange II2 againstwhich is 'positioned an annular collar I I3 peripherally shouldered toreceiverone end of a tubular skirt |I4 projecting into the casing bore81. The sleeve I||, collar ||3 and skirt 4 are all secured together as aunit. Surrounding the sleeves |08 and III and extending between theflange |09 and collar |I3 is an axially expansive A sleeve |08 isslidablycoil spring |I6. The spring ||6 is normally held undercompression and serves as the actuating member for forcibly moving thestud I2 successively away from and toward the surface of the deck plate8.

Means ls provided for releasing one end of the coil spring ||6 so as tomove the stud I2 away from the deck plate 8 so as to create the arc gaptherebetween. Positioned adjacent the lower edge of an opening II1,formed in thev side wall of the casing 51, is a pair of spaced lugs I|8bearing a pivot pin II9 upon which is journaled a latch lever |2I havinga dog |22 thereon which is engaged with the upper surface oi' the disk88. A relatively longer pair of lugs |23 are provided, spaced from thelugs |I8, which carry a pivot pin |24 and a stop pin |26 spaced from thepivot pin |24. On the pivot pin |24 is pivotally mounted a trigger |21and one section |28 of a hinged link; the other section |29 of the linkbeing attached by means of a pivot pin |3| to the latch lever |2I. Apivot pin |32 connects the two sections |28 and |29 of the hinged link.A`

torsion spring |30 urges the link section |28 against the stop pin |26.The trigger |21 is provided with an integral extension I 33 carrying atrip pin |34 which overlies an edge of the sec- 'tion 28 of the hingedlink. Plvotally mounted on a pivot pin |36, which is carried by a pairof lugs |31 positioned adjacent the lower end of the casing 51, is 'alatch lever |38 having a dog I|39 which engages the lower surface of theco1- lar II 3. The spring II6, which is under compression when thewelding head is ready for use, is therefore confined againstlongitudinal expansion by the latch dogs |22 and |39. Viewing thestructure of Figure 4, when the operator pulls the trigger |21, the trippin |34 will contact and swing the link section |28 about the latterspivot so that the center of the hinge pivot |32 will be moved out of theplane passing through the axes of all of the pivots thereby causing thehinged link to buckle and permitting the latch lever dog |22 to releaseits engagement with the disk 88. This permits the disk 88 to moveupwardly under the influence of the expanding spring II6 until the diskengages a rubber bumper I 4| seated adjacent the bottom of the casingbore 81. Movement of the disk 88 will cause a corresponding movementupwardly of the bolt 94 and consequently the ram 18 will be moved untilthe upper face of the fiange 11 impinges against the lower end of thetube 19. This raises the stud I2, as shown in Figure 6, to a positionelevated above the deck plate 8 so that the arc gap 83 is createdbetween the deck plate and the lower end of the stud.

Means is provided for conducting welding current to the stud I2 so as tocreate an electric arc between the stud and deck plate. The threaded endof the tube 19 extends upwardly beyond the.upper end of the casing 51and is engaged with one end of a tubular steel shell |42. On the shell|42 is mounted the split collar |43 formed integrally with a hollowpistol-grip handle |44; a screw |46 passing through apertured lugs |41formed on the collar |43 serving to clamp the collar securely to theshell |42. The outer end of the handle |44 is provided with a pair ofopenings through one of which passes a welding current cable |48 andthrough the other of which passes a control current cable |49. Afterentering the handle |44 the cable |48 emerges from the side thereofthrough a tubular boss ISI, as shown in Figure l, is then formed with aloop |52 and is provided at its end with a spade connector |58 whoseapertured end is secured on the shank 66 between the chuck 6| and theplug 61. The /other end of the cable |48 is connected to oneV terminal|54 of an electromagnetic contactor |56, the other terminal |51 of thecontactor being connected to one end of a conductor |58 which connectswith an output terminal of a direct current welding current generator|58. A conductor |6|, attached, at its respective ends, to the otheroutput terminal of the generator |58 and, by means of a suitable clip,to the deck plate 8, completes the welding current circuit. An actuatingsolenoid |62 drives an armature |68 in the contactor |58 to move themovable contact |64 into engagement with the fixed contact |68 so as tomake or break the circuit between the conductors |48 and |58.

Positioned within the handle |44 and electrically insulated therefrom byinsulating blocks |61 and a ilexible insulating strip |68, which aremounted on the handle by screws |68, is a pair of ilexible metallicswitch blades q|1| and |12 which, in their normal positions of rest asshown in Figure 4, are spaced apart at their free ends. 'I'he upperswitch blade |1| is provided with an extension |13, projecting beyondthe contacts |14 to which is attached, by rivets |16, a strip ofinsulating material |11. A push button |18, slidably mounted in anapertured boss |18, positioned adjacent the end of the switch blade |12,has one end thereof positioned in contact with the insulating strip |68below the said end of the switch blade |12 and the other end thereof incontact with the trigger |21 at a point thereon spaced from the triggerpivot pin |24.

Within the shell |42I and positioned adjacent the bottom thereof, is anannular iron pole piece |8| which is centrally bored to receive one endof a non-ferrous sleeve |82 which extends upwardly concentrically withthe shell. The upper end of the sleeve |82 is secured in the centralaperture of an iron disk |83 pressed into the upper end of the shell|42. The disk |83, shell |42 and pole piece |8| form, together with acylindrical iron armature |84 which is slidably mounted in the sleeve|82, a magnetic circuit. A tubular, non-ferrous, extension |86 of thearmature |84 has, at the upper end thereof, a flange |81 engageable withthe upper surface of the disk |83 so that the downward movement of thearmature 84 may not exceed a given limit and a coil spring |88, havingits lower end engaged with the amature and its upper end engaging a cap|88 which is mounted by means of threads |8I, on the upper end of thesleeve |42, serves to urge the armature toward its lower limit oftravel. A guide pin |82, secured in the cap |88 and extending into thespring |88 for substantially half of its length prevents lateralbuckling of thespring when the latter is compressed; and a vent opening|83 permits the escapel of compressed air from the interior of the capwhen the armature is4 moved upwardly. A solenoid coil |84, placed withinthe shell |42, concentric with the armature |84 serves to createmagnetic iiux in the magnetic circuit to move the armature upwardlyagainst the pressure of the spring |88.

A timer |86 is provided which, together with the magnetic contactor |56,may be placed in a position remote from the welding head such as, forinstance, on the usual portable hand truck which carries the weldinggenerator |58. The timer comprises a pair of relay contacts |81 whichmay be bridged by a movable contactor |88 carried on an armature |88which is actuated by a solenoid coil 28|. As is shown in Figure 7, thetimer includes a variable dashpot which controls the welding cycle. 'Ihedashpot, which may be one of several well-known makes obtainable in theopen market, comprises a housing 282 having in opposite sides thereofrecesses 288 and 284 which are each covered by iiexible diaphragms 286and 281 to provide a pair of separate chambers 288 and 288 inthehousing. The diaphragms are secured to thehousing by suitable pressureplates 2|| and screws '2|2. In the housing wall 2|3 separating the twochambers 288 and 288, is one or more by-pass openings 2|4, normallyclosed by a spring-pressed check valve 2|6 which opens downwardly intothe chamber 288, and a bleeder passage 2|1 into which extends a taperedblocking valve 2|8 carried on a threaded stem 2|8 tapped intol thehousing. The outer end of the stem 2|8 carries a dial 228 upon whichsuitable graduations indicating desired time settings are carried. Thelower end of the armature |88. or a rod extension of the armature, isthreadedly engaged in a hub 22| secured, together with clamp washers222, to the upper diaphragm 286. The weight of the armature |88 normallymaintains the upper diaphragm 286 in depressed condition so thatsubstantially all of the air in the upper chamber 288 is forced throughthe by-pass opening 2|4 and past the check valve 2|6 into the lowerchamber 288. When the solenoid 28| is energized it will urge thearmature |88 upwardly thereby creating a reduced pressure in the upperchamber 288 and causing the air in the lower chamber to iiow through thebleeder passage 2|1 past the blocking valve 2|8 into the upper chamber.This creates resistance to the upward movement of the armature dependingupon the rate at which the air is allowed to ow past the blocking valve.

Control current input leads 223, which are connected to a source of 110volt alternating current, are provided, one of which is connected to theupper end of each solenoid coil |62 and 28| and also to one of the timercontacts |81. The other lead 223 is connected by a conductor 224 to theupper switch blade |1|, in the handle |44, and also to one end of thesolenoid coil |84. The other conductor 226 from the coil |84 is rundirectly to the other timer contact |81. The lower switch blade |12 isconnected by a conductor 221 to the lower ends of each of the solenoidcoils |62 and 28|.

When the trigger |21 is pulled by the operator, so as to release thelatch lever |2| and permit the spring ||6 to raise the stud |2 to createthe arc gap 83, the vpushbutton |18 is simultaneously moved upwardly, asshown in Figure 6, to move the lower switch blade |12 upwardly towardthe other switch blade |1| so as to ,engage the contacts |14. Thiscloses the circuits to each of the solenoid coils |62 and 28|, causingthe former to engage the contacts |64 and |66 of the welding currentcontactor |56 so as to create the arc flame between the stud |2 and deckplate 8, and causing the latter to start the timer armature |88 in itsupward movement. As soon as the contactor |88 of the timer reaches andbridges the contacts |81, current will flow into the solenoid coil |84which will then cause the armature |84 to move upwardly against thepressure of the spring, I 88.

Means is provided, which is actuated upon movement of the armature |84,for releasing the lower end of the spring ||6 so as to plunge the end ofthe stud |2, which will now have been yof the armature, the end of onearm 23| of a bell crank which is pivotally mounted on the trigger pivotpin |24 and which has its other arm 232.extending downwardly toward thelower end of the welding head.. A rod 233 engaged at its respective endsin apertures formed in the bell crank arm 232 and in the latch lever |38to provide pivots 234 and 236 connects these parts for movementtogether. A channel-shaped guard 231 secured by suitable screws to thecasing 51 protects the latch levers and their associated parts againstexposure or damage. As soon as the trip bar 229 raises the arm 23|, theplanar alinement of the pivots |24--234-236 will be disturbed and willpermit the arm 232 to swing to its position shown by the dot and dashlines thereby permitting the latch lever |38 to swing upwardly so as tomove the latch dog |39 from below the collar ||3. As soon as thisoccurs, the sleeve will move downwardly.under the iniiuence of theexpanding spring |I6 and will carry with it the chuck assembly therebyreturning the end of the stud I2 into engagement with the deck plate 8.Simultaneously with this action, the arm 23|, in moving upwardly,contacts the insulating member |11 'of the upper switch blade, to theposition indicated by the dot and dash lines, to cause the contacts |14to separate. 'Ihis immediately deenergizes the solenoid coil |64 andopens the contacto'r contacts |64 and |66 thereby shutting on.' thewelding current. Since the contacts |14 are now separated a distancegreater than the maximum movement of the push button |18, the weldingcurrent may not be deliberately or accidently turned on by pressureagainst the trigger |21 until the welding head is again conditioned tomake the succeeding weld. This safety feature prevents the operator fromreceiving severe accidental burns or shocks. After thev weld iscompleted the welding head is lifted so as to pull the stud from thechuck. The resistance oiered by the stud to being separated from thechuck is sumcient to cause the plunger and its associated parts to bemoved toward the lower end oi the welding head thereby partiallycompressing the spring ||6 and causing resetting of the latch lever |2|.The act of placing a new stud in the chuck and pressing downwardly onthe welding head so as to iirmly seat the stud in the chuck is suicientto further compress the spring ||6 and to cause the latch dog |39 tosnap in place below the collar 3. The welding head is now fullyconditioned for the new weld with the exception of a possible adjustmentof the support should the new hole, in which the stud is to be welded,happen to vary in depth from the preceding one.

Having thus described my invention in detail, what I claim as new anddesire to secure by Letters Patent is:

l. In combination, an electric welding circuit including rst and secondmetallic members to be welded together and forming the respectiveelectrodes oi said welding circuit, a welding head including a movableram carrying said ilrst metallic member, a support, for engaging asurface adjacent said second metallic member,

carrying said welding head and adjustably extensible to primarily movesaid welding head, ram and first metallic member bodily toward or fromsaid second metallic member, unitary coniined pressure means in saidwelding head and operatively connected with said ram for successivelysecondarily moving said ram and the iirst metallic member carriedthereby into spaced relation with said second metallic member, to

establish an electric arc between the said metal-l lic member, and thenvinto contiguous relation to join said metallic members, means forreleasing said conned pressure means to move the ram and first metallicmember into spaced relation with the second metallic member, andseparate means for releasing said conilned pres-I sure means to move theram and rst metallic member toward said second metallic member.

2. In combination, an electric welding circuit including rst and secondmetallic members to be welded togetherand forming the respectiveelectrodes of said welding circuit, a welding head including a movableram carrying said iirst metallic member, a support, for engaging asurface adjacent said second metallic member, carrying said welding headand adjustably extensible to primarily move said welding head, ram andiirst metallic member bodily toward or from said second metallic member,unitary confined pressure means in said welding head and operativelyconnected with said ram for successively secondarily moving said ram andthe rst metallic member carried thereby into spaced relation with saidsecond metallic member, to establish an electric arc between the saidmetallic members, and then into contiguous relation to join saidmetallic members, manually operable means for releasing said coniinedpressure means to move the ram and first metallic member into spacedrelation with the second metallic member, means operative at the end ofa predetermined interval of time after operation of said manuallyoperable releasing means for releasing said coniined pressure means tomove the ram and first metallic member toward said second metallicmember, and means situated remote from said welding head for adjustablyvarying said interval of time.'

3. In combination, an electric welding circuit including rst and secondmetallic members to be welded together and forming the respectiveelectrodes of' said welding circuit, a welding head including a movableram carrying said first metallic member, a support, for engaging asurface adjacent said second metallic member, carrying said welding headand adjustably extensible to primarily move said welding head, ram andrst metallic member bodily toward or from said second metallic member, aunitary spring mounted in said wedling head and engaged with andexpansible to move said ram alternately in opposite directions, rst andsecond latches releasably engaging opposite ends of said spring for"other end of said spring to move the ram and first metallic member in anopposite direction toward said second metallic member, and meanssituated remote from said Welding head for actuating saidelectro-magnetic spring releasing means.

4. In combination, an electric welding circuit including first andsecond metallic members to be welded together and forming the respectiveelectrodes of said welding circuit, a welding head including a movableram carrying said iirst metallic member, a support, for engaging asurface adjacent said second metallic member, carrying said welding headand adjustably extensible to primarily move said welding head, ram andrst metallic member bodily toward or from said second metallic member, aunitary spring mounted in said welding head and engaged with andexpansible to move said ram alternately in opposite directions, firstand second latch levers pivotally mounted on said welding head andreleasably engaging opposite ends of said spring for confining saidspring under compression, a manually operable trigger pivotally mountedon said welding head and operatively connected with and to move saidfirst latch lever to release one end of said spring so as to move theram and the first metallic member into spaced relation with the secondmetallic member, an electro-magnetically actuated armature movablymounted in said'welding head, a bell crank pivotally mounted on saidwelding head operatively connected with and to move said second latchlever to release the other end of said spring so as to move the ram andrst metallic member toward the second metallic member, said bell crankhaving an arm extending into the path of movement of, and to be movedby, said armature, and means situated remote from said welding headoperatively connected with and to move said armature.

5. In combination, an electric welding circuit including anelectro-magnetically controlled contactor and first and second metallicmembers to be welded together and forming the respective electrodes ofsaid welding circuit, an electromagnetically actuated variable intervaltimer, a. welding head including a movable ram carrying said rstmetallic member, a support, for engaging a surface adjacent said secondmetallic member, carrying said welding head and adjustably extensible toprimarily move said welding head, ram and first metallic member bodilytoward or from said second metallic member, a unitary spring mounted insaid welding head and engaged with and expansible to move said ramalternately in opposite directions, first and second latch leverspivotally mounted on said welding head and releasably engaging oppositeends of said spring for confining said spring under compression, amanually operable trigger pivotally mounted on said welding head andoperatively connected with and to move said first latch lever to releaseone end of said spring so as to move the ram and the first metallicmember into spaced relation with the second metallic member, a controlswitch mounted on said welding head and connected with and to be closedby said trigger upon movement of the latter, said control switch beingincluded in control circuits for energizing said contactor to close thewelding circuit and for starting said interval timer, a bell crankpivotally mounted on said welding head operatively connected with and tomove said second latch lever to release the opposite end of said springso as to move the ram and first metallic member into engagement with thesecond metallic member, said bell crank having an arm extendingtherefrom, a solenoid coil in said welding head, an armature within andmovable by the coil upon excitation of the latter, said armature havingan extension thereof engageable with said bell crank extension so as toconnect the armature and bell crank for movement together, and a switch1n said`timer in circuit with said solenoid coil for closing an electriccircuit to said coil during operation of said timer.

6. In combination, an electric welding circuit including anelectro-magnetically controlled contactr and first and second metallicmembers to be welded together and forming the respective electrodes ofsaid welding circuit, an electromagnetically actuated variable intervaltimer, a welding head including a movable ram carrying said rst metallicmember, a support, for engaging a surface adjacent said second metallicmember, carrying said welding head and adjustably extensible toprimarily move said Welding head, ram and rst metallic member bodilytoward or from said second metallic member, a unitary spring mounted insaid welding head and engaged with and expansible to move said ramalternately in opposite directions, rst and second latch leverspivotally mounted on said welding head and releasably engaging oppositeends of said spring for coniining said spring under compression, amanually operable trigger pivotally mounted on said welding head andoperatively connected with and to move said first latch lever to releaseone end of said spring so as to move the ram and the rst metallic memberinto spaced relation with the second metallic member, a control switchmounted on said welding head and connected with and to be closed by saidtrigger upon movement of the latter, said control switch having a pairof iiexible contact arms one of which has an extension, said controlswitch being included in control circuits for energizing said contactorto close the welding circuit and for starting the operation of saidinterval timer, a solenoid coil in said welding head, an armature withinand movable by the coil upon excitation of the latter, said armaturehaving an extension thereon, a switch in said timer in circuitwith saidsolenoid coil for closing an electric circuit to said coil duringoperation of said timer, a bell crank pivotally mounted 0n said weldinghead operatively connected with and to move said second latch lever torelease the opposite end of said spring so as to move the ram and rstmetallic member toward and into engagement with the second metallicmember, said bell crank having an arm extending therefrom into the pathof movement of said armature extension so as to be engaged and moved bysaid extension upon movement of the armature, and said bell crank armbeing movable, by and upon release of said opposite end oi the spring,into engagement with said control switch extension to open said controlswitch.

7. In combination, a welding head for carrying a first metallic memberto be Welded to a second metallic member, means for positioning saidwelding head relative to said second metallic member, a singleself-propelling element in said welding head for moving said firstmetallic member in a cycle from and toward said second metallic member,and means positioned remote from said welding head for operativelyconfining the successive movement cycles of said first metallic ltallicmember, powered release mechanism in said welding head for controllingmovement of said moving element for the rst metallic member, a timerremote from said welding head for instituting power pulses atsubstantially identically spaced intervals of time after 'movements ofsaid rst metallic member away from said second metallic member, andmeans for conducting said power pulses from said timer to said poweredrelease means.

9. In combination, a welding head for carrying a ilrst metallic memberto be welded to a second metallic member, means for positioning saidwelding head relative to said second metallic member, and a singleself-propelling element in said welding head for moving said firstmetallic member in a cycle from and toward said second metallic member.l

EDWARD F. NELSON.

